1. Field of the Invention
The present invention relates to a carbon fiber composite material and a wet friction member, and particularly, the wet friction member used for a wet clutch for an automatic change gear of a vehicle and the carbon fiber composite material used for the wet friction member.
2. Description of the Prior Art
There has been conventionally a so-called carbon fiber composite material (for example, refer to Patent Document 1) in which the carbon fiber is blended as one of the wet friction member materials, and it has been known that the carbon fiber composite material exhibits excellent durability and heat resistance in a severe friction atmosphere. For example, the carbon fiber composite material is manufactured by impregnating a woven cloth or nonwoven cloth of the carbon fiber with the thermosetting resin, and heating a thermosetting resin to carbonize.
[Patent Document 1] Japanese Published Unexamined Patent Application No. H11-5850 (paragraphs 0011 to 0018)
Referring to the friction performance of the wet friction member used for the automatic change gear or the like of the vehicle, it has been known that a change of the torque or friction coefficient in the friction engaging process of a friction member and its mating member, so-called dynamic friction performance affects the generation of shock and judder or the like at the time of shift transmission. So as to suppress the generation of shock or judder conventionally, the dynamic friction performance is adjusted by the quality of the material and property of an ATF (automatic transmission fluid) additive agent or the wet friction member.
Furthermore, since the wet friction member made of the carbon fiber composite material has a surface having a smaller amount of functional groups as compared with a paper wet friction member made of a cellulose fiber and an aramid fiber or the like, the effect of the ATF additive agent conventionally used is not fully exhibited.
On the other hand, the immunity of the oil film formed by the ATF is generally increased by enhancing the porosity of the wet friction member. As a result, the dynamic friction performance of the wet friction member is improved.
However, the carbon fiber usually used for the wet friction member made of the carbon fiber composite material is inflexible as compared with fibers such as the cellulose fiber and the aramid fiber, and the fiber diameter is larger. Thereby, the average pore diameter is larger, and the average pore diameter of the paper wet friction member is several μm. On the contrary, the average pore diameter of the wet friction member made of the carbon fiber composite material is several-tens μm. As a result, even if the porosity of the wet friction member made of the carbon fiber composite material is the same as that of the paper wet friction member, it is difficult to enhance the dynamic friction performance of the wet friction member made of the carbon fiber composite material as compared with the paper wet friction member.
It is an object of the present invention to provide a wet friction member exhibiting excellent dynamic friction performance and a carbon fiber composite material used for the wet friction member.